The invention relates to a radially deformable belt ply for pneumatic tires which has at least one ring of sheet or strip material extending in the circumferential direction of the tire, and which comprises extension zones, such as undulations and/or projections or recesses, which extend transversely to the direction of rotation of the tire.
Belt plies of this kind are known (EP 0 191 124 A1) but, in this case, the ring, which is, for example, designed to be undulate, solely serves the purpose of producing the desired transverse rigidity, whereas additional strength-supporting means are provided for circumferential rigidity.
On the other hand, annular belt plies for pneumatic tires are known (DE-A-1 194 720 and DE-A-2 355 489) which are both extension- and pressure-resistant. The notches and/or recesses provided in these belt plies, which have a relatively great or deep thickness, serve the purpose of permitting the penetration of the surrounding rubber material of the pneumatic tire and, possibly, of improving the flexibility at the edges, but they should not influence the strength and rigidity in the circumferential direction. It is for this reason, that these known belt plies are not able to follow, resiliently, the linear variations of the pneumatic tire equipped with such a belt ply when it passes through the tire-tread region, with the result that pneumatic tires equipped with such belt plies wear relatively rapidly due to distinct displacements of the material from the tread region into the non-loaded circumference and due to small bending radii in the rolling humps and upright waves, and disintegrate as a result of the temperatures consequently arising in the polymer material, and also do not provide a pleasant travelling comfort. In addition, these known belt plies cannot perform the local radial deformations in the tread region from the cylindrical form of the firm belt ply, which are required in practice.